The present invention relates generally to computers and personal digital assistants, and more specifically to an integrated circuit providing both the functionality of BIOS routines and user storage.
Today, every computer and personal digital assistant uses some type of permanent memory to store the software code that provides essential low-level services, commonly called Basic Input/Output Services (BIOS), some type of storage device to provide access to an operating system that provides higher level services, and some type of storage device that allows a user to run application programs and retrieve stored data. For example, a typical configuration in a personal computer is to have the BIOS stored in an integrated circuit located on the motherboard, the operating system stored on a magnetic hard disk drive which has an I/O interface with the motherboard, and to provide volatile memory chips (RAM) into which programs or parts of programs are retrieved from a secondary storage device (e.g., hard disk drive or floppy disk drive) for operation.
While this configuration has proven to be effective, this technology has been, and continues to be, driven by the need for smaller and more powerful computers. The dramatically increasing popularity of laptop and palmtop computers, to be followed in the near future by personal digital assistants, evidences the market pressure for continued technological advances which will allow further miniaturization without sacrificing performance.
Since both magnetic hard disk drives and floppy disk drives are relatively large and somewhat susceptible to mechanical failure, they have become a target for improvement by system designers. Accordingly, one of the many results of this pressure to miniaturize was the development of solid state disk technology (SSD). The basic concept behind SSD technology is to use integrated circuits, e.g., ROMs, RAMs, and EPROMs, not only as primary system memory, but also as secondary storage so that hard and/or floppy disk drives can be eliminated. Solid state disks have the additional benefits of being smaller, more rugged and consuming less power than conventional magnetic storage.
A newer type of solid state memory, called flash memory, has recently been used in SSD applications. Flash memory components comprise arrays of electrically erasable programmable read-only memory (EEPROM) devices which can be simultaneously erased. Flash memory components have very favorable attributes for use in SSD applications including fast access, low power consumption, high reliability and relatively low cost. Unfortunately, flash devices also have the drawback of being erasable at a block level only. This constraint has conventionally relegated flash memory to the role of read-only memory, which is undesirable in devices purporting to be a substitute for secondary storage devices such as hard disk drives which provide read/write functionality.
Moreover, despite the technical advances in this area, a completely integrated solution has not yet been developed. In particular, there is a need for the various memory devices which store required code, such as the BIOS and the operating system, as well as optional code, such as a user's applications, to be integrated into a single package. This need has not yet been satisfied by today's products.